Brake fluids are composed of 3 mains components: lubricant basis 5-30% (polyglycols), solvent 60-90% (polyglycol ethers that dissolve polyglycols and all other components in such a way to obtain a single-phased fluid to provide satisfactory lubrication under all temperatures), and additives 2 to 5% (corrosion inhibitors and antioxidants).
There are 4 types of brake fluids: DOT 3, DOT 4, DOT 5, and DOT 5.1.
There are three classes of brake fluids: Glycol ethers and derivatives (DOT 3, DOT 4, DOT 5.1), mineral Oils (LHM), and silicone oils (DOT 5).
More on brake fluids is available in Advice & Proposals section.